Disposable absorbent products (e.g., diapers, feminine hygiene products, incontinence products, etc.) are subjected to one or more liquid insults, such as of water, urine, menses, or blood, during use. Many commercially available diapers allow water vapor to pass through the diaper and into the environment to lessen the amount of moisture held against the skin and reduce the chance of skin irritation and rash due to skin overhydration. To allow the passage of vapor through the diaper and into the environment while holding liquid, a “breathable” outer cover is often employed that is formed from a nonwoven web laminated to a film. The film contains a filler (e.g., calcium carbonate) that causes a series of micropores to develop in the film when stretched. The micropores form what is often referred to as “tortuous pathways” through the film. Liquid contacting one side of the film does not have a direct passage through the film. Instead, a network of microporous channels in the film prevents liquids from passing, but allows gases and water vapor to pass. One shortcoming with such microporous films is that they are generally formed from polyolefins (e.g., LLDPE), which are not biodegradable. Consequently, various attempts have been made to form microporous films from a biodegradable polymer, such as an aliphatic-aromatic copolyester. Such attempts, however, are generally designed only for a specific application and lack the wide range of flexibility in processing and physical properties often needed for films having a large number of potential uses.
As such, a need currently exists for a technique for forming biodegradable films that may be readily adapted to numerous potential applications.